Adipocytes from genetically obese (ob/ob) mice display an impaired response to beta-adrenergic stimulation, but the molecular defects have not been unequivocally identified. The expression and functional activity of the beta 1-, beta 2-, and beta 3-adrenergic receptor (AR) subtypes in white and brown adipose tissue from genetically lean and obese (ob/ob) mice were compared. Three beta 3AR transcripts of 2.1, 2.6, and 3.5 kilobases were identified in adipose tissue from lean mice by Northern blotting. All three beta 3AR mRNA species were dramatically reduced (by approximately 300-fold) in 12-week-old obese mice compared to those in lean animals. beta 1AR mRNA levels were also reduced (by approximately 4-fold) in obese mice, whereas beta 2AR mRNA levels were not significantly changed. The functional consequences of these changes in beta 3AR and beta 1AR expression were assessed by measuring beta-agonist-stimulated adenylyl cyclase activity in adipocyte plasma membranes with subtype-selective beta-adrenergic agonists and antagonists. Dose-response curves with epinephrine from lean mice were best fit to a two-component model comprised of 23% high affinity (K(act) = 1.42 x 10(-7) M) and 77% low affinity (K(act) = 1.67 x 10(-5) M) components, corresponding to activation of beta 1AR and beta 2AR conjointly, and beta 3AR, respectively. The beta 1AR-selective antagonist CGP20712A reduced the high affinity component to about 10%, whereas the nonselective beta-antagonist propranolol eliminated the high affinity component. The beta 3AR-selective agonist BRL37344 stimulated adenylyl cyclase activity in lean membranes to a slightly lesser extent than epinephrine, but was more potent (73% high affinity component; K(act) = 3.61 x 10(-8) M). In obese mice, stimulation of adenylyl cyclase by all agonists was severely blunted and was best fit to a single class of sites. Studies with CGP20712A or the beta 2AR-selective antagonist ICI118,551 indicated that this residual response was predominantly beta 2AR in character. Expression of beta AR subtypes in both brown and white adipose tissue of weanling obese mice (4-5-weeks of age) was also affected, but to a lesser extent, consistent with the progressive severity of obesity with age. Together the reduction in expression of the beta 3AR and beta 1AR impairs the beta-agonist-stimulated adenylyl cyclase response over a broad concentration range by greatly lowering the maximum stimulation and shifting the adrenergic sensitivity at low concentrations from a mixed beta 1AR/beta 2AR response to predominantly beta 2AR.

The product of the recently cloned mouse obese (ob) gene is likely to play an important role in a loop regulating the size of the adipose tissue mass. The hormonal regulation of the ob gene could affect adiposity. To investigate this point, the effect of insulin on ob gene expression was examined in cells of the 3T3-F442A preadipocyte clonal line. ob mRNA is absent from exponentially growing, undifferentiated cells as well as from confluent preadipose cells. Terminal differentiation of preadipose to adipose cells leads to the expression of ob mRNA detected by a sensitive and quantitative ribonuclease protection assay. In adipose cells, the level of ob mRNA is sensitive to insulin in the nanomolar range of concentrations with an increase from an average of 1 copy to 5-10 copies/cell. The effect of insulin was fully reversible and takes place primarily at a transcriptional level. The ob mRNA shows a rapid turnover, with a half-life of approximately 2 h in the absence or presence of insulin. The level of secreted Ob protein is also regulated by insulin. These results indicate that the ob gene is expressed in mature fat cells only and support the possibility that insulin is an important regulator of ob gene expression.

We investigated the response of leptin to short-term fasting and refeeding in humans. A mild decline in subcutaneous adipocyte ob gene mRNA and a marked fall in serum leptin were observed after 36 and 60 h of fasting. The dynamics of the leptin decline and rise were further substantiated in a 6-day study consisting of a 36-h baseline period, followed by 36-h fast, and a subsequent refeeding with normal diet. Leptin began a steady decline from the baseline values after 12 h of fasting, reaching a nadir at 36 h. The subsequent restoration of normal food intake was associated with a prompt leptin rise and a return to baseline values 24 h later. When responses of leptin to fasting and refeeding were compared with that of glucose, insulin, fatty acids, and ketones, a reverse relationship between leptin and beta-OH-butyrate was found. Consequently, we tested whether the reciprocal responses represented a causal relationship between leptin and beta-OH-butyrate. Small amounts of infused glucose equal to the estimated contribution of gluconeogenesis, which was sufficient to prevent rise in ketogenesis, also prevented a fall in leptin. The infusion of beta-OH-butyrate to produce hyperketonemia of the same magnitude as after a 36-h fast had no effect on leptin. The study indicates that one of the adaptive physiological responses to fasting is a fall in serum leptin. Although the mediator that brings about this effect remains unknown, it appears to be neither insulin nor ketones.

We have determined the crystal structure of apo-CusF, a periplasmic protein involved in copper and silver resistance in Escherichia coli. The protein forms a five-stranded beta-barrel, classified as an OB-fold, which is a unique topology for a copper-binding protein. NMR chemical shift mapping experiments suggest that Cu(I) is bound by conserved residues H36, M47, and M49 located in beta-strands 2 and 3. These residues are clustered at one end of the beta-barrel, and their side chains are oriented toward the interior of the barrel. Cu(I) can be modeled into the apo-CusF structure with only minimal structural changes using H36, M47, and M49 as ligands. The unique structure and metal binding site of CusF are distinct from those of previously characterized copper-binding proteins.

Obesity is a risk factor for postmenopausal breast cancer and is associated with poor prognosis. Leptin, a cytokine synthesized in adipose tissue, has been implicated as a link between obesity and breast cancer. In the present study, the effects of leptin on cell proliferation and proteins associated with leptin signaling and/or breast cell growth were investigated in ER-positive, MCF-7, T47-D and MDA-MB-361, and ER-negative, MDA-MB-231 and SK-BR-3, breast cancer cell lines. MDA-MB-361 and SK-BR-3 also overexpress HER2/neu. For proliferation assays, 96-well plates were used and for protein determinations cells were synchronized in 6-well plates for 18-24 h in serum-free medium. Leptin was added at 0, 5, 10, 25, 50 and 100 ng/ml for 24 and 48 h. For Western blot analyses, protein extracts were probed for Ob-Rb, Ob-R, leptin, Jak2, PI3K, Stat3, p-Stat3, PCNA, cyclin D1, Cox-2, VEGF, Bcl-2, Bcl-xL, Bax, insulin, IGF-I, IGFBP3, IGF-IRalpha, aromatase, CYP1A1 and CYP1B1. Overall, except for MCF-7 cells, leptin stimulated proliferation in all lines. MCF-7 cells expressed higher levels of Ob-Rb, Jak2, PI3K, Stat3 and p-Stat3 in a dose-dependent manner to 50 ng/ml at 24 h; and IGF-IRalpha increased at 24 h. Cyclin D1 and Cox-2 levels increased with leptin treatment. Higher CYP1B1 expression was observed at both 24 and 48 h. In MDA-MB-231 cells, p-Stat3 and Bcl-xL were increased at 48 h; whereas PCNA and cyclin D1 expression increased in leptin-treated cells at 24 and 48 h. In T47-D cells, Jak2 and Stat3 were elevated at higher leptin concentrations at 24 and 48 h. However, p-Stat3 and PCNA demonstrated an increase only in 48-h leptin-treated cells. Furthermore, cyclin D1 exhibited higher expression at both 24 and 48 h, while Bcl-xL expression was lower with increasing concentrations of leptin at 48 h. In MDA-MB-361 cells, Ob-Rb and VEGF increased at 24 and 48 h; whereas PI3K, Stat3, PCNA and insulin levels increased in leptin-treated MDA-MB-361 cells after 48 h. Bcl-2 and IGF-IRalpha were decreased at 24 h and a dose-dependent increase at 48 h was noted. Higher expression of CYP1B1 was observed with leptin for 24 h. In SK-BR-3 cells, Ob-R increased at both 24 and 48 h. A similar trend was found for IGF-I and IGFBP3 expression. Higher levels of Jak2 and PI3K were observed after 24 h. Interestingly, there was a gradual increase of leptin expression at 24 h, but a gradual decrease at 48 h in relation to the dose of leptin. In contrast, PCNA and IGF-IRalpha showed a decline at 24 h and an increase at 48 h. Elevated levels of cyclin D1, VEGF and Bax were detected at 48 h in cells and increased Cox-2 expression was observed at 24 h. These data indicate that leptin may influence breast cancer development in relation to ER status as well as to the presence or absence of HER2. Continued study on leptin may be helpful for a better understanding of breast cancer development in obese women.

Cardiotrophin (CT-1) signals through gp130 and the LIF receptor (LIFR) and plays a major role in cardiac, neurological, and liver biology. We report here that CT-1 is also expressed within bone in osteoclasts and that CT-1 is capable of increasing osteoblast activity and mineralization both in vitro and in vivo. Furthermore, CT-1 stimulated CAAT/enhancer-binding protein-delta (C/EBP delta) expression and runt-related transcription factor 2 (runx2) activation. In neonate CT-1(-/-) mice, we detected low bone mass associated with reduced osteoblasts and many large osteoclasts, but increased cartilage remnants within the bone, suggesting impaired resorption. Cultured bone marrow (BM) from CT-1(-/-) mice generated many oversized osteoclasts and mineralized poorly compared with wildtype BM. As the CT-1(-/-) mice aged, the reduced osteoblast surface (ObS/BS) was no longer detected, but impaired bone resorption continued resulting in an osteopetrotic phenotype in adult bone. CT-1 may now be classed as an essential osteoclast-derived stimulus of both bone formation and resorption.

Cysteine proteases play an important part in human pathobiology. This report shows the participation of cathepsin L (CatL) in adipogenesis and glucose intolerance. In vitro studies demonstrate the role of CatL in the degradation of the matrix protein fibronectin, insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF-1R), essential molecules for adipogenesis and glucose metabolism. CatL inhibition leads to the reduction of human and murine pre-adipocyte adipogenesis or lipid accumulation, protection of fibronectin from degradation, accumulation of IR and IGF-1R beta-subunits, and an increase in glucose uptake. CatL-deficient mice are lean and have reduced levels of serum glucose and insulin but increased levels of muscle IR beta-subunits, fibronectin and glucose transporter (Glut)-4, although food/water intake and energy expenditure of these mice are no less than their wild-type littermates. Importantly, the pharmacological inhibition of CatL also demonstrates reduced body weight gain and serum insulin levels, and increased glucose tolerance, probably due to increased levels of muscle IR beta-subunits, fibronectin and Glut-4 in both diet-induced obese mice and ob/ob mice. Increased levels of CatL in obese and diabetic patients suggest that this protease is a novel target for these metabolic disorders.

Leptin (ob protein) and glucagon-like peptide-1-(7-36) amide (GLP-1) are peptides recently proposed to be involved in the regulation of food intake. Although the ability of exogenous leptin and GLP-1 to modulate consummatory behavior is consistent with the suggestion that these peptides are endogenous regulatory agents, central administration of these peptides may have aversive side effects, which could explain the anorexia. In the present experiment, exposure to a saccharine taste was immediately followed by central administration of leptin or GLP-1 to determine if these drugs could produce a conditioned taste aversion (CTA) in rats. At doses equated for producing comparable reductions in short-term food intake, GLP-1, but not leptin, generated a robust CTA. Although leptin caused no aversion, this peptide was the only drug to cause relatively long-term reductions in food consumption (16 h) and body weight (24 h). Hence, the results indicate that central GLP-1 produces aversive side effects, and it is argued that these nonspecific effects may explain the anorectic actions of GLP-1.

Bone remodeling is a tightly controlled mechanism in which osteoblasts (OB), the cells responsible for bone formation, osteoclasts (OC), the cells specialized for bone resorption, and osteocytes, the multifunctional mechanosensing cells embedded in the bone matrix, are the main actors. Increased oxidative stress in OB, the cells producing and mineralizing bone matrix, has been associated with osteoporosis development but the role of autophagy in OB has not yet been addressed. This is the goal of the present study. We first show that the autophagic process is induced in OB during mineralization. Then, using knockdown of autophagy-essential genes and OB-specific autophagy-deficient mice, we demonstrate that autophagy deficiency reduces mineralization capacity. Moreover, our data suggest that autophagic vacuoles could be used as vehicles in OB to secrete apatite crystals. In addition, autophagy-deficient OB exhibit increased oxidative stress and secretion of the receptor activator of NFKB1 (TNFSF11/RANKL), favoring generation of OC, the cells specialized in bone resorption. In vivo, we observed a 50% reduction in trabecular bone mass in OB-specific autophagy-deficient mice. Taken together, our results show for the first time that autophagy in OB is involved both in the mineralization process and in bone homeostasis. These findings are of importance for mineralized tissues which extend from corals to vertebrates and uncover new therapeutic targets for calcified tissue-related metabolic pathologies.

Formation of new adipocytes from precursor cells contributes to adipose tissue expansion and obesity. In this study, we asked whether p38 mitogen-activated protein kinase (MAPK) pathway regulates normal and pathological adipogenesis. In both dietary and genetically (ob/ob) obese mice, adipose tissues displayed a marked decrease in p38MAPK activity compared with the same tissues from lean mice. Furthermore, p38MAPK activity was significantly higher in preadipocytes than in adipocytes, suggesting that p38MAPK activity decreases during adipocyte differentiation. In agreement with an inhibitory role of p38MAPK in this process, we found that in vitro inhibition of p38MAPK, with the specific inhibitor PD169316, increased the expression of adipocyte markers in several cellular models, from embryonic to adult stages. Importantly, the expression of adipocyte markers was higher in p38MAPKalpha knockout cells than in their wild-type counterparts. Phosphorylation of C/EBPbeta, which enhances its transcriptional activity, is increased after p38MAPK inhibition. Finally, either inhibition or disruption of p38MAPK increased peroxisome proliferator-activated receptor (PPAR)gamma expression and transactivation. Rescue of p38MAPK in knockout cells reduced PPARgamma activity to the low basal level of wild-type cells. We demonstrate here, by using multipronged approaches involving p38 chemical inhibitor and p38MAPKalpha knockout cells, that p38MAPK plays a negative role in adipogenesis via inhibition of C/EBPbeta and PPARgamma transcriptional activities.

Significant correlations between obesity and incidence of various cancers have been reported. Obesity, considered a mild inflammatory process, is characterized by a high level of secretion of several cytokines from adipose tissue. These molecules have disparate effects, which could be relevant to cancer development. Among the inflammatory molecules, leptin, mainly produced by adipose tissue and overexpressed with its receptor (Ob-R) in cancer cells is the most studied adipokine. Mutations of leptin or Ob-R genes associated with obesity or cancer are rarely found. However, leptin is an anti-apoptotic molecule in many cell types, and its central roles in obesity-related cancers are based on its pro-angiogenic, pro-inflammatory and mitogenic actions. Notably, these leptin actions are commonly reinforced through entangled crosstalk with multiple oncogenes, cytokines and growth factors. Leptin-induced signals comprise several pathways commonly triggered by many cytokines (i.e., canonical: JAK2/STAT; MAPK/ERK1/2 and PI-3K/AKT1 and, non-canonical signaling pathways: PKC, JNK and p38 MAP kinase). Each of these leptin-induced signals is essential to its biological effects on food intake, energy balance, adiposity, immune and endocrine systems, as well as oncogenesis. This review is mainly focused on the current knowledge of the oncogenic role of leptin in breast cancer. Additionally, leptin pro-angiogenic molecular mechanisms and its potential role in breast cancer stem cells will be reviewed. Strict biunivocal binding-affinity and activation of leptin/Ob-R complex makes it a unique molecular target for prevention and treatment of breast cancer, particularly in obesity contexts.

Type 2 diabetes mellitus (T2DM) is associated with a high incidence of non-alcoholic fatty liver disease (NAFLD) related to obesity and insulin resistance. Currently, medical interventions for NAFLD have focused on diet control and exercise to reduce body weight, and there is a requirement for effective pharmacological therapies. Sodium-glucose cotransporter 2 (SGLT2) inhibitors are oral antidiabetic drugs that promote the urinary excretion of glucose by blocking its reabsorption in renal proximal tubules. SGLT2 inhibitors lower blood glucose independent of insulin action and are expected to reduce body weight because of urinary calorie loss. Here we show that an SGLT2 inhibitor ipragliflozin improves hepatic steatosis in high-fat diet-induced and leptin-deficient (ob/ob) obese mice irrespective of body weight reduction. In the obese mice, ipragliflozin-induced hyperphagia occurred to increase energy intake, attenuating body weight reduction with increased epididymal fat mass. There is an inverse correlation between weights of liver and epididymal fat in ipragliflozin-treated obese mice, suggesting that ipragliflozin treatment promotes normotopic fat accumulation in the epididymal fat and prevents ectopic fat accumulation in the liver. Despite increased adiposity, ipragliflozin ameliorates obesity-associated inflammation and insulin resistance in epididymal fat. Clinically, ipragliflozin improves liver dysfunction in patients with T2DM irrespective of body weight reduction. These findings provide new insight into the effects of SGLT2 inhibitors on energy homeostasis and fat accumulation and indicate their potential therapeutic efficacy in T2DM-associated hepatic steatosis.

Stearoyl-CoA desaturase (SCD) has recently been shown to be a critical control point of lipid partitioning and body weight regulation. Lack of SCD1 function significantly increases insulin sensitivity in skeletal muscles and corrects the hypometabolic phenotype of leptin-deficient ob/ob mice, indicating the direct antilipotoxic action of SCD1 deficiency. The mechanism underlying the metabolic effects of SCD1 mutation is currently unknown. Here we show that SCD1 deficiency reduced the total ceramide content in oxidative skeletal muscles (soleus and red gastrocnemius) by approximately 40%. The mRNA levels and activity of serine palmitoyltransferase (SPT), a key enzyme in ceramide synthesis, as well as the incorporation of [14C]palmitate into ceramide were decreased by approximately 50% in red muscles of SCD1-/- mice. The content of fatty acyl-CoAs, which contribute to de novo ceramide synthesis, was also reduced. The activity and mRNA levels of carnitine palmitoyltransferase I (CPT I) and the rate of beta-oxidation were increased in oxidative muscles of SCD1-/- mice. Furthermore, SCD1 deficiency increased phosphorylation of AMP-activated protein kinase (AMPK), suggesting that AMPK activation may be partially responsible for the increased fatty acid oxidation and decreased ceramide synthesis in red muscles of SCD1-/- mice. SCD1 deficiency also reduced SPT activity and ceramide content and increased AMPK phosphorylation and CPT I activity in muscles of ob/ob mice. Taken together, these results indicate that SCD1 deficiency reduces ceramide synthesis by decreasing SPT expression and increasing the rate of beta-oxidation in oxidative muscles.

Protein tyrosine phosphatase 1B (PTP1B) contributes to leptin resistance by inhibiting intracellular leptin receptor signaling. Mice with whole body or neuron-specific deletion of PTP1B are hypersensitive to leptin and resistant to diet-induced obesity. Here we report a significant increase in PTP1B protein levels in the mediobasal hypothalamus (P = 0.003) and a concomitant reduction in leptin sensitivity following 28 days of high-fat (HF) feeding in rats. A significant increase in PTP1B mRNA levels was also observed in rats chronically infused with leptin (3 microg/day icv) for 14 days (P = 0.01) and in leptin-deficient ob/ob mice infused with leptin (5 microg/day sc for 14 days; P = 0.003). When saline-infused ob/ob mice were placed on a HF diet for 14 days, an increase in hypothalamic PTP1B mRNA expression was detected (P = 0.001) despite the absence of circulating leptin. In addition, although ob/ob mice were much more sensitive to leptin on a low-fat (LF) diet, a reduction in this sensitivity was still observed following exposure to a HF diet. Taken together, these data indicate that hypothalamic PTP1B is specifically increased during HF diet-induced leptin resistance. This increase in PTP1B is due in part to chronic hyperleptinemia, suggesting that hyperleptinemia is one mechanism contributing to the development of leptin resistance. However, these data also indicate that leptin is not required for the increase in hypothalamic PTP1B or the development of leptin resistance. Therefore, additional, leptin-independent mechanisms must exist that increase hypothalamic PTP1B and contribute to leptin resistance.

The skeleton is the most common metastatic site for breast cancer, with bone metastasis causing pain as well as risk of pathological fractures. Interaction between tumors and the bone microenvironment creates a vicious cycle that accelerates both bone destruction and cancer progression. This study is the first to analyze the soluble factors secreted by breast tumor-associated osteoblasts (TAOBs), which are responsible for promoting cancer progression. The addition of CXCL5 (chemokine (C-X-C motif) ligand 5), present in large amounts in TAOB-condition medium (TAOB-CM), mimicked the inductive effect of TAOB-CM on breast cancer epithelial-mesenchymal transition, migration and invasion. In contrast, inhibition of CXCL5 in OBs decreased TAOB-mediated cancer progression. Inducement of MCF-7 and MDA-MB-231 cancer progression by TAOB-derived CXCL5 is associated with increased Raf/MEK/ERK activation, and mitogen- and stress-activated protein kinase 1 (MSK1) and Elk-1 phosphorylation, as well as Snail upregulation. Activation of Elk-1 facilitates recruitment of phosphorylated MSK1, which in turn enhances histone H3 acetylation and phosphorylation (serine 10) of Snail promoter, resulting in Snail enhancement and E-cadherin downregulation. Moreover, mice treated with anti-CXCL5 antibodies showed decreased metastasis of 4T1 breast cancer cells. Our study suggests that inhibition of CXCL5-mediated ERK/Snail signaling is an attractive therapeutic target for treating metastases in breast cancer patients.

OBJECTIVE

Leptin responsive neurons play an important role in energy homeostasis, controlling specific autonomic, behavioral, and neuroendocrine functions. We have previously identified a population of leptin receptor (LepRb) expressing neurons within the dorsomedial hypothalamus/dorsal hypothalamic area (DMH/DHA) which are related to neuronal circuits that control brown adipose tissue (BAT) thermogenesis. Intra-DMH leptin injections also activate sympathetic outflow to BAT, but whether such effects are mediated directly via DMH/DHA LepRb neurons and whether this is physiologically relevant for whole body energy expenditure and body weight regulation has yet to be determined.

METHODS

We used pharmacosynthetic receptors (DREADDs) to selectively activate DMH/DHA LepRb neurons. We further deleted LepRb with virally driven cre-recombinase from DMH/DHA neurons and determined the physiological importance of DMH/DHA LepRb neurons in whole body energy homeostasis.

RESULTS

Neuronal activation of DMH/DHA LepRb neurons with DREADDs promoted BAT thermogenesis and locomotor activity, which robustly induced energy expenditure (p < 0.001) and decreases body weight (p < 0.001). Similarly, intra-DMH/DHA leptin injections normalized hypothermia and attenuated body weight gain in leptin-deficient ob/ob mice. Conversely, ablation of LepRb from DMH/DHA neurons remarkably drives weight gain (p < 0.001) by reducing energy expenditure (p < 0.001) and locomotor activity (p < 0.001). The observed changes in body weight were largely independent of food intake.

CONCLUSIONS

Taken together, our data highlight that DMH/DHA LepRb neurons are sufficient and necessary to regulate energy expenditure and body weight.

In the mouse olfactory system, the anatomical locations of olfactory sensory neurons (OSNs) roughly correlate with their axonal projection sites along the dorsal-ventral (D-V) axis of the olfactory bulb (OB). Here we report that an axon guidance receptor, Neuropilin-2 (Nrp2), and its repulsive ligand, Semaphorin-3F (Sema3F), are expressed by OSNs in a complementary manner that is important for establishing olfactory map topography. Sema3F is secreted by early-arriving axons of OSNs and is deposited at the anterodorsal OB to repel Nrp2-positive axons that arrive later. Sequential arrival of OSN axons as well as the graded and complementary expression of Nrp2 and Sema3F by OSNs help to form the topographic order along the D-V axis.

BACKGROUND

An important step in obesity research involves identifying neurobiological underpinnings of nonfood reward processing unique to specific subgroups of obese individuals.

METHODS

Nineteen obese individuals seeking treatment for binge eating disorder (BED) were compared with 19 non-BED obese individuals (OB) and 19 lean control subjects (LC) while performing a monetary reward/loss task that parses anticipatory and outcome components during functional magnetic resonance imaging. Differences in regional activation were investigated in BED, OB, and LC groups during reward/loss prospect, anticipation, and notification.

RESULTS

Relative to the LC group, the OB group demonstrated increased ventral striatal and ventromedial prefrontal cortex activity during anticipatory phases. In contrast, the BED group relative to the OB group demonstrated diminished bilateral ventral striatal activity during anticipatory reward/loss processing. No differences were observed between the BED and LC groups in the ventral striatum.

CONCLUSIONS

Heterogeneity exists among obese individuals with respect to the neural correlates of reward/loss processing. Neural differences in separable groups with obesity suggest that multiple, varying interventions might be important in optimizing prevention and treatment strategies for obesity.

The association between inflammation and endoplasmic reticulum (ER) stress has been observed in many diseases. However, if and how chronic inflammation regulates the unfolded protein response (UPR) and alters ER homeostasis in general, or in the context of chronic disease, remains unknown. Here, we show that, in the setting of obesity, inflammatory input through increased inducible nitric oxide synthase (iNOS) activity causes S-nitrosylation of a key UPR regulator, IRE1α, which leads to a progressive decline in hepatic IRE1α-mediated XBP1 splicing activity in both genetic (ob/ob) and dietary (high-fat diet-induced) models of obesity. Finally, in obese mice with liver-specific IRE1α deficiency, reconstitution of IRE1α expression with a nitrosylation-resistant variant restored IRE1α-mediated XBP1 splicing and improved glucose homeostasis in vivo. Taken together, these data describe a mechanism by which inflammatory pathways compromise UPR function through iNOS-mediated S-nitrosylation of IRE1α, which contributes to defective IRE1α activity, impaired ER function, and prolonged ER stress in obesity.

Metabolic syndrome (MS), defined as central obesity, hyperinsulinemia, insulin resistance, hypertension, dyslipidemia and glucose intolerance, has been associated with inflammatory biomarkers and cardiovascular diseases. This study was carried out on three groups of women; lean controls, moderately obese with MS (OB-MS) and morbidly obese with MS (MOB-MS). The main objectives were: 1. to analyze the plasma levels of total and acylated ghrelin, peptide YY(3-36) (PYY(3-36)), cholecystokinin (CCK), gastrin and insulin levels under basal conditions and in response to a standard mixed meal, and 2. to elucidate the relationship between the plasma levels of these gut peptides and metabolic syndrome parameters. Plasma levels of the gut hormones were measured by radioimmunoassays at time 0 just before the meal and at 30, 60 and 120 min after a meal ingestion. Traditional lipid profile and high-sensitivity C reactive protein (hs-CRP), the strongest biomarker of inflammation were also determined in OB-MS and MOB-MS. When compared to OB-MS, MOB-MS exhibited much higher anthropometric parameters such as waist circumference, higher fat mass and higher plasma levels of low density lipoprotein-cholesterol (LDL-C) and hs-CRP. Both these obese groups revealed significantly higher values of body mass index (BMI), fat mass, total cholesterol (TC), LDL-C, fasting glucose, fasting insulin, insulin resistance (IR) calculated from homeostatic model assessment (HOMA) and hs-CRP compared to the values recorded in lean subjects. Fasting PYY(3-36) level was lower, while fasting acylated ghrelin was higher in MOB-MS than in OB-MS. Plasma total and acylated ghrelin levels were significantly lower in OB-MS compared to lean women. In MOB-MS women the fasting PYY(3-36) levels were lower compared to lean controls and OB-MS, whilst postprandially in both OB-MS and MOB-MS, it was much lower than in lean women. The fasting plasma levels of total and acylated ghrelin and their postprandial decrease were significantly smaller in both obese groups compared to lean subjects. Plasma hs-CRP levels correlated positively with BMI, waist circumference, fat mass, fasting glucose, HOMA IR and fasting active ghrelin, whilst it negatively correlated with plasma fasting and total ghrelin. Moreover, plasma fasting acylated ghrelin correlated positively with fat mass. Fasting total ghrelin correlated positively with BMI, HDL-C and negatively with HOMA IR. We conclude that MS features of obesity are closely related to fasting and postprandial alterations of concentrations of PYY(3-36), CCK and ghrelin, suggesting that determination of gut hormones controlling food intake might be considered as a valuable tool to assess the progression of MS to comorbidities of obesity.

In the adult rodent brain, neural stem cells (NSCs) persist in the ventricular-subventricular zone (V-SVZ) and the subgranular zone (SGZ), which are specialized niches in which young neurons for the olfactory bulb (OB) and hippocampus, respectively, are generated. Recent studies have significantly modified earlier views on the mechanisms of NSC self-renewal and neurogenesis in the adult brain. Here, we discuss the molecular control, heterogeneity, regional specification and cell division modes of V-SVZ NSCs, and draw comparisons with NSCs in the SGZ. We highlight how V-SVZ NSCs are regulated by local signals from their immediate neighbors, as well as by neurotransmitters and factors that are secreted by distant neurons, the choroid plexus and vasculature. We also review recent advances in single cell RNA analyses that reveal the complexity of adult neurogenesis. These findings set the stage for a better understanding of adult neurogenesis, a process that one day may inspire new approaches to brain repair.

Fatty liver is common in nonalcoholic, obese individuals and in lean people who consume alcohol chronically. Although fatty liver is typically benign, a subset of individuals with steatosis develop steatohepatitis and eventually cirrhosis. The disparate outcomes of fatty liver suggest that it reflects a generally beneficial, adaptive response to obesity or alcohol-related stress, but may also increase hepatocyte vulnerability to other challenges. Thus, both protective factors (e.g., Bcl-2 and Bcl-xL) and factors that promote hepatocyte death by apoptosis (e.g., Bax) or necrosis (e.g., UCP2) may be increased in fatty livers. To evaluate this possibility, hepatocyte apoptosis, necrosis, and the expression of factors that regulate cellular viability were assessed in two models of fatty liver (i.e., genetically obese [ob/ob] mice and ethanol [EtOH]-fed lean mice). Findings in mice with fatty livers were compared with lean, control mice that did not have hepatic steatosis. Immunohistochemistry showed striking induction of hepatocyte proteins that promote (e.g., Bax) and inhibit (e.g., Bcl-2 and Bcl-xL) apoptosis in both groups with fatty liver. Both models of fatty liver also increased hepatic transcripts for UCP2, a mitochondrial uncoupling protein, and the protein itself was induced in ob/ob hepatocytes. Despite the up-regulation of factors that threaten cell viability, hepatocyte death was not increased in either ob/ob or EtOH-fed mice, confirming that the liver's protective responses were sufficient under the conditions studied. However, if UCP2 induction reduces the efficiency of adenosine triphosphate (ATP) synthesis, this initially harmless response might enhance the vulnerability of hepatocytes to necrosis.

Small doses of the opiate antagonist naloxone selectively abolished overeating in genetically obese mice (ob/ob) and rats (fa/fa). Elevated concentrations of the naturally occurring opiate beta-endorphin were found in the pituitaries of both obese species and in the blood plasma of the obese rats. Brain levels of beta-endorphin and Leu-enkephalin were unchanged. These data suggest that excess pituitary beta-endorphin may play a role in the development of the overeating and obesity syndrome.

Skeletal growth is tightly coupled to energy balance via complex and incompletely understood mechanisms. Leptin-deficient ob/ob mice are obese and develop multiple pathologies associated with the metabolic syndrome. Additionally, ob/ob mice have skeletal abnormalities. The objective of this study was to evaluate the effects of leptin deficiency and long duration selective central leptin repletion via recombinant adeno-associated virus-leptin (rAAV-lep) gene therapy on bone in growing ob/ob mice. The ob/ob mice were injected in the hypothalamus with either rAAV-lep or rAAV-GFP (control vector). Treated ob/ob and untreated wild-type (WT) mice were then maintained on a normal diet for 15 weeks. In a second experiment, similarly treated mice along with a group of pair-fed mice were maintained for 30 weeks. Leptin was not detected in blood of either rAAV-lep- or rAAV-GFP-treated mice although rAAV-lep-treated mice displayed leptin transgene expression in the hypothalamus. As expected, rAAV-lep normalized body weight and food intake. Compared to WT mice, rAAV-GFP-treated ob/ob mice had decreased femoral length (by 1.6 mm or 10%, P<0.001), decreased total femur bone volume (by 3.3 mm(3) or 19%, P<0.001), but increased cancellous bone volume in the distal femur (by 0.04 mm(3) or 60%, P<0.09) and lumbar vertebrae (by 0.26 mm(3) or 118%, P<0.001). Treatment with rAAV-lep rescued the ob/ob skeletal phenotype by increasing femoral length and total bone volume, and decreasing femoral and vertebral cancellous bone volume, so that at 15 weeks post-rAAV-lep injection the ob/ob mice no longer differed from WT mice. No further skeletal changes in either the femur or lumbar vertebra were observed at 30 weeks post-rAAV-lep administration. The results suggest that hypothalamic leptin functions as an essential permissive factor for normal bone growth.